JP3986406B2 - Non-contact tonometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-contact tonometer that measures intraocular pressure by compressing a fluid and spraying it on an eye to be examined and detecting a deformed state of the cornea, and more specifically, detecting a pulse wave based on pulse fluctuation, The present invention relates to a non-contact tonometer that measures intraocular pressure in association with detected pulse waves and intraocular pressure fluctuations.
[0002]
[Prior art]
Intraocular pressure has fluctuations synchronized with blood pulse fluctuations, but when measured randomly with a non-contact tonometer in time, it is unknown which part of the pulse fluctuations are measured, and accurate measurement results Is difficult to obtain. In view of this, a tonometer has been proposed in which a pulse wave based on pulse fluctuations is detected by a pulse wave detector and an intraocular pressure corresponding to (synchronized with) a desired phase position of the pulse wave is measured (for example, see Patent Document 1). .
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-102174
[Problems to be solved by the invention]
In the tonometer described above, for example, in order to enable intraocular pressure measurement corresponding to a peak position of a certain pulse wave, a change in pulse wave (pulse fluctuation) is based on the period of the pulse wave detected before that. The timing of intraocular pressure measurement is determined by predicting a pulse wave peak that comes next from the pulse wave detected immediately before, which occurs periodically. In the case of a subject whose changes in pulse wave are periodically stable, the pulse wave is expected by predicting the timing of intraocular pressure measurement based on the pulse wave obtained in this way in advance. The intraocular pressure measurement can be made to correspond to the phase position with high accuracy.
[0005]
However, in the case of a subject having an arrhythmia symptom, the change in pulse wave is lost. At this time, if the measurement is executed assuming that the pulse wave is periodically changed as described above, the measurement does not correspond to the original phase of the pulse wave, and the reliability of the measurement result is poor. Further, when the change of the pulse wave is missed, an error occurs in the determination of the period of the pulse wave, so that an error is likely to occur in the determination of the next measurement timing.
[0006]
In view of the above-described problems of the prior art, the present invention provides an eye corresponding to a desired phase position according to a subject whose pulse wave is stable and a subject whose pulse wave is unstable such as an arrhythmia. It is an object of the present invention to provide a non-contact tonometer that can appropriately perform pressure measurement.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) Having a pulse wave detector for detecting the pulse wave of the subject and measuring intraocular pressure corresponding to the intended phase position of the pulse wave based on the pulse wave signal detected by the pulse wave detector to the non-contact intraocular pressure gauge, a first determining means for determining a desired to previously detected period of the pulse wave than the measurement timing corresponding to the phase position of a pulse wave based, a certain pulse wave Second determining means for determining a measurement timing corresponding to a desired phase position based on a change in the pulse wave signal, and selecting means for selecting the first determining means and the second determining means. Features.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a present Example is described based on drawing. FIG. 1 is a schematic external view of a non-contact tonometer according to the present invention.
On the base 13, a moving table 14 having a measuring unit 15 at the top is mounted so as to be horizontally movable. The moving table 14 is moved by operation of a joystick 19. Further, by operating the rotary knob of the joystick 19, the measuring unit 15 is moved in the up / down / left / right direction and the front / rear direction.
[0009]
A face support unit 16 for supporting the subject's face is fixed to the base 13. The face support unit 16 includes a chin base 10 that is fixed to the support base 16a and can be adjusted in height in the vertical direction, and a forehead support portion 17 that is attached to the upper portions of the two columns 16b. The forehead support 17 has a shape along the curve of the subject's forehead. A pulse wave detector 18 for detecting the pulse wave of the subject is provided at the center of the forehead pad 17. Also, two forehead rubbers 17 a are attached to the forehead support 17 on the left and right sides of the pulse wave detector 18. The forehead rubber 17a is disposed at an appropriate distance from the pulse wave detector 18 so that blood flows stably when the subject's forehead is fixed and ischemia does not occur in the forehead.
[0010]
The pulse wave detector 18 includes a light emitting unit and a light receiving unit. Blood hemoglobin contained in human blood has a strong absorption spectrum for light in a certain wavelength band. Blood hemoglobin changes in proportion to the amount of blood flowing through the blood vessels. Therefore, when light of a certain wavelength is emitted from the light emitting part, the detection light reflected from the bone through the skin part of the forehead surface changes according to the amount of change in hemoglobin that changes with the change in blood vessel capacity. The pulse wave of the subject can be detected by changing the intensity of the detection light into an electric signal.
[0011]
FIG. 2 is a diagram illustrating a schematic side configuration of a fluid ejection mechanism disposed in the measurement unit 15 and a schematic configuration of a tonometer control system. Reference numeral 1 denotes a cylinder for air compression, which is provided inclined with respect to the horizontal line of the tonometer main body. 2 is a piston, 3 is a rotary solenoid, and when charge (current, voltage) as drive energy is applied to the rotary solenoid 3, it is moved upward along the cylinder 1 to the piston 2 via the arm 4 and the connecting rod 5. Push up. The air compressed in the air compression chamber 11 that communicates with the cylinder portion 1 as the piston 2 rises is ejected from the nozzle 6 toward the cornea of the eye E. The rotary solenoid 3 is provided with a coil spring (not shown), and when the applied charge is cut, the piston 2 that has been lifted by the biasing force in the downward direction of the coil spring is lowered and returned to the initial position.
[0012]
A transparent glass plate 7 holds the nozzle 6 and transmits observation light, alignment light, and the like. The glass plate 7 is a side wall of the air compression chamber 11. A transparent glass plate 9 is provided on the back surface of the nozzle 6 and constitutes the rear wall of the air compression chamber 11 and transmits observation light and alignment light. Behind the glass plate 9 is an optical system 8 for observation and alignment described later. A pressure sensor 12 detects the pressure in the air compression chamber 11.
[0013]
Reference numeral 20 denotes a control unit for the pressure detection processing circuit 21 for the pressure sensor 12, the signal detection processing circuit 22 for the photodetector 56 of the corneal deformation detection optical system, which will be described later, and the one-dimensional position detection element 57 for the working distance detection. A signal detection processing circuit 26, an image processing circuit 27 for the CCD camera 35, a pulse wave detection processing circuit 28 for the pulse wave detector 18, and a drive circuit 23 for driving the rotary solenoid 3 are connected. An input unit 25 is provided with a switch 25a for selecting a measurement mode.
[0014]
FIG. 3 is a principal view of the upper-view optical system of the non-contact tonometer. The eye image illuminated by the infrared illumination light source 30 forms an image on the CCD camera 35 via the beam splitter 31, the objective lens 32, the beam splitter 33 and the filter 34. The filter 34 transmits light from the light source 30 and the alignment light source 40 and has a non-transmission characteristic to light from an LED 50 for detecting corneal deformation described later. The image formed on the CCD camera 35 is displayed on the monitor 36.
[0015]
Reference numeral 40 denotes an alignment infrared LED. The infrared light projected via the projection lens 41 is reflected by the beam splitter 31 and projected onto the eye to be examined from the front. The corneal bright spot formed at the apex of the cornea by the LED 40 forms an image on the CCD camera 35 via the beam splitter 31 to the filter 34 and is used for alignment detection in the vertical and horizontal directions.
Reference numeral 45 denotes a fixation target projection LED. The light of the fixation target 46 illuminated by the LED 45 passes through the projection lens 47 and is then reflected by the beam splitter 33 toward the eye E. The measurement is performed with the fixation target 46 fixed.
[0016]
Reference numeral 50 denotes an infrared LED for detecting corneal deformation. The light emitted from the LED 50 is made into a substantially parallel light beam by the collimator lens 51 and projected onto the cornea of the eye to be examined. The light reflected by the cornea passes through a filter 53 having a non-transmission characteristic with respect to the light of the light receiving lens 52, the light source 30, and the light source 40, and then is reflected by a beam splitter 54 and passes through a pinhole plate 55 to detect light. The light is received by the device 56. The corneal deformation detection optical system is arranged so that the amount of light received by the photodetector 56 is maximized when the eye to be examined is in a predetermined deformed state (flat state).
[0017]
The corneal deformation detection optical system also serves as a part of the working distance detection optical system, and the light projected from the LED 50 and reflected by the cornea forms an index image that is a virtual image of the LED 50. The light of the index image passes through the light receiving lens 52, the filter 53, and the beam splitter 54 and enters the one-dimensional position detection element 57 such as a PSD or a line sensor. When the eye to be examined (cornea) moves in the working distance direction, the index image by the LED 50 also moves the one-dimensional position detecting element 57, so that the control unit 20 obtains the working distance information from the one-dimensional position detecting element 57 based on the output signal. obtain.
[0018]
The operation of the non-contact tonometer having the above configuration will be described. The examiner fixes the eye to be examined using the chin rest 60 and instructs the subject so that the forehead of the subject contacts the forehead support portion 17. When the subject positions the forehead so as to hit the two forehead rubbers 17a, the forehead also comes into contact with the pulse wave detector 60 located at the center thereof. An output signal from the pulse wave detector 60 is input to the pulse wave detection processing circuit 28. The pulse wave detection processing circuit 28 adjusts the level (gain) of the output signal from the pulse wave detector 18 and then outputs it to the control unit 20.
[0019]
After fixing the eye to be examined, the examiner moves the measuring unit 15 based on the alignment information displayed on the monitor 36 to adjust the alignment. An alignment completion signal is obtained when the index image detected by the CCD camera 35 and the index image detected by the one-dimensional position detection element 57 are within the allowable ranges. When measuring in synchronization with an arbitrary phase position of the pulse wave, the control unit 20 determines the timing of the phase position (described later), outputs a signal for driving the solenoid 3, and executes the measurement. By driving the solenoid 3, the piston 2 rises and compressed air is blown from the nozzle 6 toward the eye cornea. The cornea is gradually deformed by the blowing of air. When the cornea reaches the applanation state, the maximum amount of light enters the photodetector 56. The controller 20 obtains the pressure signal from the pressure sensor 12 when the maximum amount of light is incident on the photodetector 56 or when the signal from the photodetector 56 shows a peak, and this is converted into an intraocular pressure value. Convert.
[0020]
Here, in the tonometer of the present embodiment, it is assumed that the pulse wave changes periodically, and based on the pulse wave cycle obtained in advance, it corresponds to the initial phase position of the next pulse wave. There are prepared a first measurement mode for measuring intraocular pressure by determining the measurement timing, and a first measurement mode for measuring intraocular pressure by determining the initial phase position of the pulse wave from the change of the pulse wave signal. The first measurement mode and the second measurement mode are switched by a measurement mode selection switch 25a.
[0021]
First, the first measurement mode will be described. When the first measurement mode is set, the control unit 20 acquires the pulse wave signal from the pulse wave detection processing circuit 28, and whether or not the usable condition is satisfied for the pulse wave signal (the pulse wave signal is stable) Whether or not it is obtained) is determined as follows.
[0022]
The pulse wave signal usable condition can be determined by determining the pulse wave peak (the pulse wave peak here can be determined from the slope of the rising edge of the waveform signal, the signal level, etc. by looking at the entire waveform signal in one pulse fluctuation. ) Detection time and the height of the pulse wave peak. Either of these may be used, but the determination with higher accuracy can be made by using both. As shown in FIG. 4, the detection time (cycle) from the first pulse wave peak to the second pulse wave peak for three cycles of the pulse wave waveform signal obtained sequentially from the start of pulse wave detection is T1, The detection time (cycle) from the second pulse wave peak to the third pulse wave peak is T2. Here, when both change time Th = | T1-T2 | becomes Th> 10 ms, it is determined as a time error of the pulse wave waveform signal and cannot be used.
[0023]
The height of the first pulse wave peak (height from the bottom) is defined as P1, the height P2 of the second pulse wave peak P2, and the height P3 of the third pulse wave peak. Each peak fluctuation rate is calculated by Pa = P1 / P2, Pb = P2 / P3, and Pc = P1 / P3. As a result, when all of Pa, Pb, and Pc do not fall within the range of 0.9 to 1.1, it is determined that the pulse wave waveform signal has a peak error and cannot be used.
[0024]
FIG. 5 shows an example of measuring intraocular pressure in synchronization with the phase position of the pulse wave peak. When a usable pulse wave waveform signal is obtained for three cycles of the sequentially obtained pulse wave waveform signal, the control unit 20 determines the timing when the pulse wave peak comes next. The signal S1 indicates the timing when the pulse wave peak comes next after the usable pulse wave waveform signal is obtained. The timing of the signal S1 in this embodiment is determined by the period of two pulse wave peaks detected immediately before. That is, after the pulse wave peaks Pk1, Pk2, and Pk3 satisfying the usable conditions are obtained, the timing of the next pulse wave peak pk4 is determined from the period Ta1 of Pk2 and Pk3 immediately before. Further, the timing of the pulse wave peak pk5 that comes after the pulse wave peak pk4 is determined from the period Ta2 of Pk3 and Pk4 immediately before that. By obtaining a usable pulse waveform signal in this way, the timing of the next pulse wave peak is determined. A signal R indicates an alignment completion signal. When both the alignment completion signal R and the signal S1 are obtained, the solenoid drive signal S3 is output. By driving the solenoid 36 by the signal S3, the compressed air is blown from the nozzle 6 to the eye to be examined as described above, and the intraocular pressure measurement is executed.
[0025]
In order to adjust the intraocular pressure measurement timing to the phase position of the pulse wave peak with higher accuracy, the applanation detection time Tapl from when the solenoid drive signal 3 is output until the cornea is flattened by air injection is considered. Then, it is preferable to output the solenoid drive signal S3 at a timing increased by the time Tapl. The time Tapl may be set using an average intraocular pressure value in the first measurement of the same eye, and set based on the previous intraocular pressure measurement in the second and subsequent measurements. it can.
[0026]
When measuring pulse wave synchronization, a “SAMP” mark 61 is displayed on the screen of the monitor 36 as shown in FIG. When a pulse wave peak that satisfies the usable condition is obtained, the heart mark 63 is lit for 0.5 seconds. If the pulse wave peak is continuously obtained, the heart mark 63 appears to blink. If the heart mark 63 blinks periodically, it can be determined that the pulse wave is stably obtained.
[0027]
Next, the second measurement mode will be described. The second measurement mode differs from the first measurement mode in the method for determining the measurement timing of S1. When measuring intraocular pressure in synchronization with the phase position of the pulse wave peak, it is not based on the pulse wave cycle obtained in advance as in the first measurement mode, but at the time when the pulse wave peak is obtained ( Alternatively, the intraocular pressure measurement is started at a certain time after the other phase position is obtained. The control unit 20 determines that the pulse wave peak is obtained when the following four conditions are satisfied (see FIG. 7).
[0028]
Condition 1: The waveform signal of the pulse wave starts to rise from the bottom and rises for 100 ms or more.
Condition 2: The level V0 when the waveform of the pulse wave satisfying the condition 1 shows a peak is set to 100%, and then lowered to 95%.
Condition 3: The peak level of the waveform satisfying the condition 2 is equal to or greater than the specified value Lo, and the amplitude (height from the bottom) is 50% or more with respect to the amplitude of the previous peak. However, the amplitude condition is excluded from the peak detected for the first time.
Condition 4: Condition 3 is satisfied, and the interval time Tp from the previous peak is within 0.5 to 1.5 s. However, this condition is excluded for the peak detected for the first time.
[0029]
If it is determined that there is a pulse wave peak under the above conditions, the time point when the level V0 is detected is determined as the measurement timing, and the signal S1 is output. Similarly to the first measurement mode, when both the alignment completion signal R and the signal S1 are obtained, the solenoid drive signal S3 is output and the intraocular pressure measurement is executed. The level V0 is detected when the level reaches 95% of the pulse wave peak, but since this is a slight shift in time, it can be regarded as a pulse wave peak.
[0030]
In the case of a subject whose pulse wave is not stable, such as an arrhythmia, the intraocular pressure measurement synchronized with the pulse wave can be performed more appropriately using the second measurement mode than the first measurement mode described above. When the subject is known in advance to have an arrhythmia, or when the blinking display of the heart symbol 63 is irregular on the display of the monitor 36 shown in FIG. 5, the first measurement mode is set by the switch 25a. To the second measurement mode.
[0031]
In the above description, the measurement is performed in synchronization with the phase position of the pulse wave peak. However, the measurement may be performed in synchronization with the pulse wave bottom or the intermediate position of the pulse wave (intermediate position of the pulse wave amplitude). .
[0032]
【The invention's effect】
As described above, according to the present invention, the intraocular pressure corresponding to the intended phase position according to the subject whose pulse wave is stable and the subject whose pulse wave is unstable such as arrhythmia. Each measurement can be performed appropriately.
[Brief description of the drawings]
FIG. 1 is a schematic external view of a non-contact tonometer.
FIG. 2 is a diagram illustrating a schematic side configuration of a liquid ejecting mechanism and a schematic configuration of a tonometer control system.
FIG. 3 is a diagram showing the main part of the upper optical system of a non-contact tonometer.
FIG. 4 is a diagram for explaining a method by which a control unit determines whether an input pulse wave signal satisfies a use condition (whether or not a pulse wave signal is stably obtained).
FIG. 5 is a diagram showing an example of measuring intraocular pressure in synchronization with the phase position of a pulse wave peak.
FIG. 6 is a diagram when a “SAMP” mark is displayed on a monitor screen;
FIG. 7 is a diagram illustrating a method in which a control unit determines whether or not a pulse wave peak has been obtained for an input pulse wave signal.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylinder part 2 Piston 3 Rotary solenoid 15 Measurement part 16 Face support unit 17 Forehead support part 18 Pulse wave detector 20 Control part 25 Input part 28 Pulsation detection processing circuit 35 CCD camera

Claims (1)

Non-contact having a pulse wave detector for detecting the pulse wave of the subject and measuring the intraocular pressure corresponding to the intended phase position of the pulse wave based on the pulse wave signal detected by the pulse wave detector in Shikime圧meter, a first determining means for determining the period of intended for pulse wave detected earlier than the measurement timing corresponding to the phase position of a pulse wave based and intended certain pulse wave A second determining unit that determines a measurement timing corresponding to the phase position based on a change in the pulse wave signal; and a selecting unit that selects the first determining unit and the second determining unit. Non-contact tonometer.

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